If spending hours upon hours in the gym never seemed to interest you, then Kate Upton's trainer David Kirsch might become your new best friend. Kirsch thinks the perfect bikini body can be obtained by doing short, intense workouts.

In fact, he believes a 30-minute workout is better than a 60-minute one, Harper Bazaar magazine reports. Upton's trainer said that the key thing to remember is "quality over quantity" when going after fitness goals.

"First and foremost you need to identify a reasonable realistic goal," Kirsch said. "Are you a newbie, someone who was fit and just took the holiday off? Where are you starting?"

Kirsch is the founder of David Kirsch Wellness and the Madison Square Club in New York City where actress Liv Tyler and Upton regularly go to. The celebrity trainer said he thinks setting fitness goals is important so people don't set themselves up for a "fitness failure."

Kirsch said once a person sets their goal(s) then they can really get into their fitness regimen.   

"For me, the way I go about training all of my clients is by using short bursts of interval training - it's the most effective for burning calories as well as for cardiovascular health and making you stronger," he said.

"There's less time to be bored and distracted and it gives you more access to working out - you can fit in snippets throughout the day," Kirsch added. "You aren't resting in between, checking your phone or chatting."

He explained that it's crucial for a person to do several different quick workouts that will incorporate strength training, cardio, toning and fat-burning all at once. One of his go-to circuits for clients includes a back-to-back sequence of pushups, planks, squats, shadow boxing and crunches.

Besides working with Kirsch, the Sports Illustrated model also has a personal trainer. Back in July Justin Gelband dished to Shape magazine that the 21-year-old keeps her curves in check with intense workout sessions and a fairly healthy diet.

"Since the first day I met her, she wanted to come in and change the industry by saying curves are sexy," Gelband said at the time. "She's such a great model for all the young girls out there."

He said Upton follows a program he created called ModelFIT. The program combines Zumba, a type of high-energy Latin dance, with marital arts, Pilates, yoga and capoeira. The regimen helps women strengthen, stretch, and tone their entire body as well as flatten abs and firm thighs.